In this lesson
Compare an original deck with a smaller copy and note any changes to pictures, captions and editing.
Example
A smaller onboarding package
Use a practice deck with your laptop picture, three process shapes and the captioned clip from media-recording-and-captions. Complete that lesson first if you need the clip, or start here with pictures and compatibility. Save Onboarding-Original.pptx and make Onboarding-Delivery.pptx before compressing media or deleting cropped picture data.
How it works
File size depends on embedded images, media and fonts, not just slide count. A smaller copy is useful only if it still meets the viewing, editing and accessibility needs of its audience.
Compatibility Checker identifies potential older-format losses, but it does not test every browser, device or codec. Saving to legacy PPT may turn editable objects into pictures; retaining PPTX is usually the better source strategy.
Steps
Save a separate delivery copy and record both files’ sizes from the operating-system file information. Write the measurement units, because MB and bytes are not interchangeable labels.
Select the original picture and use Picture Format › Compress Pictures where available. Choose a delivery resolution suitable for your screen and inspect the picture at full-slide viewing size.
Remove cropped picture data only in the delivery copy if that reduction is useful. Reopen the image crop controls afterward and confirm you intentionally accepted losing the hidden image areas.
On Windows, inspect File › Info › Compress Media. Before using it, retain the caption source and original deck: Microsoft documents that embedded subtitles and alternate audio tracks are lost in this operation. Skip it when those tracks are required.
On Windows, run File › Info › Check for Issues › Check Compatibility if a recipient requests an older format. Review the reported losses, then create a separate legacy-format test copy instead of replacing the PPTX source.
Reopen the delivery and test copies. Play the clip, check captions, read the three process labels and try editing the objects. Record the new size and any differences in your comparison checklist.
Try it yourself
- Make a comparison checklist with Original, Delivery and Legacy test columns. For each record file size, image readability, caption availability and whether the process shapes remain editable.
- If compression removed a required caption track, restore the original media or return to the uncompressed delivery copy. Keep the smaller copy only when all required delivery behaviours pass.
Show expected result
- The original source remains available; every reported size is measured rather than promised in advance.
- The checklist records missing captions or converted objects, and the chosen delivery file keeps the features its audience needs.
If something goes wrong
- The file barely shrinks after compressing one picture.
- Check whether video, audio or embedded fonts account for most of the size. Compare the original and delivery copies. Stop lowering picture quality if images are not the main source of file size.
- Captions vanish after optimisation.
- Return to the uncompressed original clip and reinsert its caption track if needed. Keep that version when embedded subtitles or alternate audio tracks are required; Compress Media can remove them.
Quick check
Try these questions after the exercise. Check the result in your app before marking the lesson complete.
Choose an answer for all 3 questions to check your understanding.
Optional: try it with Copilot
If you have Copilot, try this after the exercise. Keep the original file and compare its suggestions with your own result.
Create a comparison checklist for original and compressed practice decks. Include measured size, image readability, captions and editable objects; leave every pass/fail blank for actual testing.
More from Microsoft
These Microsoft guides cover the tools used in this lesson.
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